Reboot the computer and tap the F8 key repeatedly to see if you have the Repair Console on Advanced Boot Options menu.
If so, run Startup Repair repeatedly If not you can find or download a Win7 REpair CD or Installation DVD to write to flash stick using WinToFlash.
Boot it to run Startup Repair repeatedly after making sure WIn7 or it's 100mb boot partition (preferred) is marked Active: Partition - Mark as Active
Another option would be to run factory recovery from it's partition at boot if you still have the Recov partition. Or clean reinstall using Win7 installer from flash stick: Reinstalling Windows 7